The invention relates to a guide roller for continuous-casting plants, which is subdivided into a plurality of roller portions aligned with one another, adjacent roller portions being connected to a roller journal carrying a support bearing, and the roller portion which terminates in a roller journal engaging into a recess of the adjacent roller portion.
In plants for the continuous casting of metal strands, in which the ratio of strand width to strand thickness is very high, such as, for example, slabs or thin slabs, the strand guide rollers supporting and guiding the strand along its wide sides are subdivided into a plurality of roller portions with aligned axes.
In the continuous-casting plant known from AT-B 290 750, the roller bodies arranged next to one another are mounted on a common axis, and between the individual roller bodies engage support members or shaft holders which are supported on curved longitudinal girders or on rear-engaging beams or on a fixed frame structure, as is customary on continuous-casting plants of this type. Supporting all the roller bodies individually necessitates an extremely large number of bearings on the common axis, the susceptibility of this construction to faults being very high because of the complicated supply of lubricant to the many bearing points.
AT-B 335 093 discloses a strand guide roller constituting the pre-characterising clause, which is formed by a plurality of roller portions aligned with and identical to one another and which is braced by means of a tie passing centrally through all the roller portions. The asymmetric design of the strand guide roller results in this strand guide roller experiencing a creeping movement in the axial direction, which leads to increased wear in the mountings and on the roller portions adjacent to the connection. The same problem arises in an embodiment of the strand guide roller according to DE-C 27 42 570.
DE-B 24 20 514 likewise discloses a guide roller for continuous-casting plants which is multiply mounted and is subdivided into identical roller portions. Here, too, the above-described disadvantages due to the asymmetric design of the guide roller become evident.
DE-A-24 23 224 discloses a subdivided multiply mounted guide roller for continuous-casting plants, which is formed by roller portions lined up alternately with one another in alignment and by shaft stubs carrying bearings. The multiplicity of components of complicated design results in increased manufacturing costs and high outlay in terms of assembly.
It is also known to arrange a plurality of solid-body rollers next to one another and to mount them individually, on both sides, on a fixed frame structure of the continuous-casting plant. As a result, necessarily, two journal bearings with a large space requirement are positioned next to one another and the billet is not supported in this region, thus causing the billet shell to bulge out and giving rise to increased internal expansions in the billet. The susceptibility of the billet to cracking is therefore increased.
The invention aims to avoid the disadvantages and difficulties described, and its set object is to propose a strand guide roller, by means of which creeping movements of the strand guide roller in the axial direction and distortions dependent on the thermal conditions in the strand guide roller are avoided. Another aim of the invention is to form the strand guide roller from components to be manufactured cost-effectively and to design,it for easy maintenance.
This object is achieved, according to the invention, in that a roller portion which is adjacent on both sides of roller portions either is provided at its two ends with roller journals carrying support bearings, and these roller journals engage in recesses of the adjacent roller portions, or is provided at its two ends with recesses, and roller journals, carrying support bearings, of the adjacent roller portions engage into these recesses. Due to the symmetrical design of a central roller portion flanked by further roller portions, the load exerted by the weight of the strand on the entire strand guide roller results in an optimum, specifically minimized and symmetrical flexion of the strand guide roller. A preferred embodiment is formed by a centrally arranged roller portion which is provided at its two ends by roller journals carrying support bearings. The number of the adjacent roller portions is the same on both sides for reasons of symmetry.
In a refinement which is simple in manufacturing terms and has low wear, the roller journal of a roller portion is mounted in the recess of the adjacent roller portion in sealed-off mountings, preferably sealed-off slide bushes or spherical bearings. It thus becomes possible for relative movements, above all thermally induced axial movements and tilting movements resulting from the roller flexion, to take place without any stress.
According to a further refinement of the invention, adjacent roller portions are secured against rotation and axial displacements relative to one another by means of a positive bracing device, preferably having a clamping sleeve passing through them transversely to their longitudinal extent. The clamping-sleeve connection, in particular, proves to be of simpler design and more cost-effective than the tie bracing known from AT-B 335 093. Moreover, the clamping sleeve fixes by positive connection and thereby prevents a possible crawling movement with friction and wear in the journal connections. Crawling movements of this kind occur, during the normal operation of a plant, due to the uneven wear of the roller surface as a result of the casting of slabs of different width. Preferably, the bracing device passes through the mounting of the roller journal of a roller portion in the recess of the adjacent roller portion.
When the cast strand runs through the supporting and guiding structure of the continuous-casting plant, the guide rollers are subjected to thermal loading due to linear contact with the hot strand and to the heat radiated from the latter. In order to cool the guide rollers, the roller portions have a central coolant duct, and the coolant ducts of adjacent roller portions are connected to coolant cross-over sleeves.